The present invention relates to improvements in multiple layer metal gaskets, alternatively called multi-layer metal or MLM gaskets.
Gaskets are often used as seals between mating mechanical components. One common application involves gasket placement between the engine block and the cylinder head of an internal combustion engine. Cylinder head gaskets typically extend around the cylinder bores to provide combustion seals, retaining the high temperature/high pressure gases of combustion within the cylinder bores. At the same time, the gaskets also seal fluid flow openings such as coolant and oil openings to prevent undesirable mixing of the latter engine fluids. In addition, such gaskets prevent leakage by sealing the areas around the bolts which connect the cylinder head and the engine block. The gasket bears the compressive load from a bolted connection of the mechanical components and relies upon such compression to provide a seal.
Diesel cycle internal combustion engines ("diesel engines") have higher compression ratios, and typically sustain compression forces in the combustion chamber greater than those sustained by conventional Otto cycle internal combustion engines ("gas engines"). Therefore, the combustion seal provided by the diesel engine gasket must sustain such higher pressures. The majority of cylinder head gaskets used in heavy duty diesel engines are of a composite type, employing a steel plate sandwiched between two fibrous composite layers.
Diesel engines are also distinguished from gas engines in that diesels typically employ cylinder liners which define the cylinder bores. These liners extend beyond a sealing surface of the engine block by a variable distance known as "cylinder stand-up". To compensate for the variation in cylinder stand-up, composite gaskets have incorporated wire rings between the steel plates which are located over the cylinder liners. Tightening of the cylinder head bolts flattens the wire rings to define a combustion seal around each cylinder bore between the head and the block.
Multi-layer metal gaskets are a known alternative to composite gaskets and offer superior performance and durability characteristics in gas engines. However, such gaskets are not well suited for use in diesel engines, because they do not adequately accommodate the variations in cylinder stand-up. Known multi-layer metal gaskets also tend to have a large number of constituent elements, often including complexly shaped metal formings. One complex forming commonly used with a wire ring is an outer plate which wraps around the ring, defining a ring retainer with a U-shaped cross section.
It is desired to provide a multi-layer metal gasket for use with both diesel and gas engines which provides a superior combustion seal. It is also desired to provide a multi-layer metal gasket with superior sealing capabilities having a minimum number of constituent elements, and with each element being relatively simple in form.